Piping Size

[NukeeZoid]

Hi guys,

Just wanted to ask a few quick questions...

What are the piping sizes for cat-back exhaust systems like the Fuijitsubo RM01A etc...

I know the stock Type-R exhaust is 2.3inch in piping... so are these systems bigger or maintain a similar size but use highflow and less restrictive silencers and exhaust boxes to gain power?

I only ask because the guys at JFA Exhaust told me the best size to go with for the DC5 is 2.5inches with a custom backbox. This will give the highest gains...

I'm looking to get it done because it'll cost alot less than buying a branded cat-back system, and will probably give me more gains due to higher exhaust flow.



Thanks ahead of time for any replies!

 

[jd5]

Hi guys,

Just wanted to ask a few quick questions...

What are the piping sizes for cat-back exhaust systems like the Fuijitsubo RM01A etc...

I know the stock Type-R exhaust is 2.3inch in piping... so are these systems bigger or maintain a similar size but use highflow and less restrictive silencers and exhaust boxes to gain power?

I only ask because the guys at JFA Exhaust told me the best size to go with for the DC5 is 2.5inches with a custom backbox. This will give the highest gains...

I'm looking to get it done because it'll cost alot less than buying a branded cat-back system, and will probably give me more gains due to higher exhaust flow.



Thanks ahead of time for any replies!

Goin a few inches bigger than the original diameters is ok, but not too big, as in 3inch, which is more for cars churning big time HP. The idea is to increase flow without loosing too much of back pressure. Branded exhaust systems are built in away where the above is in a way guaranteed, but you end up paying big bucks.

For custom, the problem is, not everyone is good at building one. I have seen a custom pipes in which the pipe diameters are inconsistent/bad welding, etc. But as far as JFA is concern, they're probably good, judging by GTI4740's gain from a custom built exhaust + intake in a thread posted earlier... haha!

Perhaps the Otais here could advise you further...

 

[NukeeZoid]

just wanted to share some info i found on the singapore Integra forums:

Are you a muff?

Exhaust gases leave the engine under extremely high pressure. If we allowed exhaust gasses escape to the atmosphere directly from the exhaust port, you can well imagine how loud and cop-attracting the noise would be. For the same reason gunshots are loud, engine exhaust is loud. Sure, it might be cool to drive around on the street with that testosterone producing, chest-thumping, 150 decibel roar coming from your car… for about 5.3 seconds. (Not 5.2 or 5.4 seconds… 5.3.) Even the gentleman's gentleman has gotta use a muffler, or system of mufflers, on their exhaust.

Again, you may hear a few SPMT's tell you that "Borla mufflers make horsepower!" Or "An engine needs some backpressure to run properly!" Nonsense. A muffler can no more "make" horsepower than Wile E. Coyote can catch roadrunners. Any technician with any dyno experience will tell you that the best mufflers are no mufflers at all!

Pipe Sizing

We've seen quiet a few "experienced" racers tell people that a bigger exhaust is a better exhaust. Hahaha… NOT.

As discussed earlier, exhaust gas is hot. And we'd like to keep it hot throughout the exhaust system. Why? The answer is simple. Cold air is dense air, and dense air is heavy air. We don't want our engine to be pushing a heavy mass of exhaust gas out of the tailpipe. An extremely large exhaust pipe will cause a slow exhaust flow, which will in turn give the gas plenty of time to cool off en route. Overlarge piping will also allow our exhaust pulses to achieve a higher level of entropy, which will take all of our header tuning and throw it out the window, as pulses will not have the same tendency to line up as they would in a smaller pipe. Coating the entire exhaust system with an insulative material, such as header wrap or a ceramic thermal barrier coating reduces this effect somewhat, but unless you have lots of cash burning a hole in your pocket, is probably not worth the expense on a street driven car.

Unfortunately, we know of no accurate way to calculate optimal exhaust pipe diameter. This is mainly due to the random nature of an exhaust system -- things like bends or kinks in the piping, temperature fluctuations, differences in muffler design, and the lot, make selecting a pipe diameter little more than a guessing game. For engines making 250 to 350 horsepower, the generally accepted pipe diameter is 3 to 3 ? inches. Over that amount, you'd be best off going to 4 inches. If you have an engine making over 400 to 500 horsepower, you'd better be happy capping off the fun with a 4 inch exhaust. Ah, the drawbacks of horsepower. The best alternative here would probably be to just run open
exhaust!

Thats why for the Type-R making roughly 220bhp....my guess is that a 2.5 inch exhaust would be the best sizing.

 

[lazybass]

advantage: large piping diameter will cause less vibration n noise lvel on engine n exhst systm due to low back pressure, giving a smooth rev on rpm...

 

[Rider]

2.7 inch d best for high end...

---------- Post added at 09:07 PM ---------- 6 hour anti-bump limit - Previous post was at 08:52 PM ----------

if u want toda header i have one ofer at 2500 only..

 

[NukeeZoid]

i just got a de-cat for my header. works like a charm.

anyways....will budget myself for custom 2.5 inch exhaust...

 

[hahf]

2.5inch will be good, and pls be aware that 2.5inch is outer diameter, where inner diameter will become about 2.3inch.

 

[NukeeZoid]

2.5inch will be good, and pls be aware that 2.5inch is outer diameter, where inner diameter will become about 2.3inch.

so does that mean that the stock 2.3 inch piping is actually 2.1 inch in diameter on the inside? :hmmmm:

 

[NukeeZoid]

also...how much have you custom guys paid for 2.5 inch piping + custom straight flow back box?

I'm looking to get mine done at Jaafar....and i think the price is going to come out to be roughly RM1300 - 1400 with 2.5 inch piping + silencer + back box....